Electrographic printers and copiers utilizing developer comprising toner, carrier, and other components use a developer mixing apparatus and related processes for mixing the developer and toner used during the printing process. The term “electrographic printer,” is intended to encompass electrophotographic printers and copiers that employ dry toner developed on an electrophotographic receiver element, as well as ionographic printers and copiers that do not rely upon an electrophotographic receiver. The electrographic apparatus often incorporates an electromagnetic brush station or similar development station, to develop the toner to a substrate (an imaging/photoconductive member bearing a latent image), after which the applied toner is transferred onto a sheet and fused thereon.
As is well known, a toner image may be formed on a photoconductor by the sequential steps of uniformly charging the photoconductor surface in a charging station using a corona charger, exposing the charged photoconductor to a pattern of light in an exposure station to form a latent electrostatic image, and toning the latent electrostatic image in a developer station to form a toner image on the photoconductor surface. The toner image may then be transferred in a transfer station directly to a receiver, e.g., a paper sheet, or it may first be transferred to an intermediate transfer member (ITM) and subsequently transferred to the receiver. The toned receiver is then moved to a fusing station where the toner image is fused to the receiver by heat and/or pressure.
Development stations require replenishment of toner into the developer sump to replace toner that is deposited on the photoconductor or receiver. In development stations utilizing a carrier, this toner must be mixed uniformly with the carrier. Replenishment has been done at a single location in the developer sump, but this has lead to high concentrations of low-charge toner in one area of the sump, which tends to produce a dark streak on the image or receiver, or produces non-uniform areas in an image.
The present invention corrects the problem of non-uniform mixing. The apparatus and related methods transport and mix the toner efficiently when needed, maintaining the correct proportions necessary to produce the high quality prints or powder coatings required by consumer demand. The following invention solves the current problems with developer mixing so that the mixer will work in a wide variety of situations and with different types of toners, powders, or particles.